Underwater acoustic sources may have a number of different applications including, for example, marine geology, acoustic oceanography, ocean acoustic tomography, underwater positioning and navigation, underwater communications, and sound propagation research. Among these traditional oceanographic applications the sound sources may be used to measure sea water parameters such as, for example, ocean temperature and currents. Further applications may include the measurement of ocean floor characteristics such as, for example, an acoustic bottom impedance. Additional applications may also include, without limitation, positional measurements of underwater instruments, research experiments on underwater sound propagation, and testing and calibration of underwater acoustic receiver arrays.
Underwater acoustic sources located, for example, at the ocean floor, may be advantageously used for determining bottom sediment acoustic properties. Measurement of such sediment acoustic properties may be desirable for developing and using low and mid frequency sonar devices in shallow water. For such purposes, a sound source may be placed on a moving underwater autonomous vehicle (UAV) to study sound propagation in shallow water or for use in a moving target source to test and calibrated underwater survival systems.
In all such uses, a desirable sound source should be compact and efficient, use little power, and emit a well calibrated, highly frequency-coherent signal over a large frequency band. Such characteristics may be especially desirable for an underwater sound source deployed for extended periods of time.